As this type of apparatus, for example, there is proposed an apparatus provided with an actuator having a locking mechanism which is connected to a camshaft, which is configured to change a relative phase of the camshaft with respect to a crankshaft with in a predetermined change range, and which is to set the relative phase at a locking position. Particularly, here, it is disclosed that an unlock mode for releasing a lock pin of the locking mechanism is performed if oil pressure of the lock pin is predicted from the number of engine revolutions and an elapsed time from the start of an engine and if it is determined that the oil pressure has sufficiently increased (refer to Patent document 1).
Alternatively, there is proposed a valve timing adjusting apparatus which is provided with: a first rotating body; a second rotating body; and a lock pin configured to restrict relative rotation between the first rotating body and the second rotating body, and which is configured not to flow oil to a retard chamber until the restriction of the first rotating body and the second rotating body by the lock pin is completely released (refer to Patent document 2).
Alternatively, there is proposed a technology in a valve timing adjusting apparatus provided with: a vane rotor configured to rotate with a camshaft; a housing configured to rotate relatively with the vane rotor; and a locking mechanism configured to regulate the relative rotation between the vane rotor and the housing, wherein oscillation between the housing and the vane rotor is increased by increasing torque variation of the camshaft, causing the lock pin to be easily removed (refer to Patent document 3).
Alternatively, there is proposed a technology in a cam phase actuator provided with: a first rotating body configured to rotate synchronously with a crankshaft; a second rotating body fixed to the camshaft; and a locking mechanism configured to lock the second rotating body at a first relative angle with respect to the first rotating body, wherein lock pin release control is performed only upon advance-angle control if it is determined to be in a lock state, thereby reducing the delay of an advance-angle operation by the lock pin release control (refer to Patent document 4).